The median nerve begins near the armpit, where branches from the lateral and medial cords of the brachial plexus join. It then travels down the arm to supply many of the muscles that bend the wrist and fingers, as well as important thumb muscles and sensation on the thumb side of the hand.

Location

Forms from a lateral root and a medial root of the brachial plexus
Starts beside the axillary artery near the shoulder and armpit
Travels down the front-inner part of the upper arm without supplying a major upper-arm muscle
Crosses the front of the elbow and continues between forearm muscles
Enters the hand through the carpal tunnel at the wrist

Function

Helps bend the wrist and several finger joints
Powers muscles that turn the palm downward
Helps the thumb move across the palm for pinch and grip
Carries sensation from the thumb, index finger, middle finger and part of the ring finger on the palm side

The nerve starts in the shoulder region, but symptoms are often felt much farther down the arm.

Why It Matters at the Shoulder

Carpal tunnel syndrome is the best-known median nerve problem, but it is not the only place the nerve can be affected. An injury to the brachial plexus or its medial and lateral cords can change median nerve function before the nerve reaches the elbow or wrist.

That distinction matters because tingling in the hand does not automatically identify where the nerve is irritated. Clinicians compare the symptom pattern with neck movement, strength, reflexes and sensation.

Common Problems

Carpal tunnel syndrome at the wrist
Pronator syndrome or other less common forearm compression
Brachial plexus injury near the neck or shoulder
Laceration or trauma along the arm

Symptoms That May Need Assessment

Persistent numbness or tingling in the thumb-side fingers
Loss of pinch strength or difficulty opposing the thumb
Hand weakness after a neck, shoulder, arm or wrist injury
Symptoms that are worsening or disturbing sleep regularly

Sudden major weakness, loss of feeling after trauma or a cold or discoloured hand needs prompt medical assessment.

Brachial plexus — the nerve network where the median nerve begins
Musculocutaneous nerve — another terminal branch from the lateral cord
Referred neck and arm symptoms — one reason hand symptoms need broader assessment

References

StatPearls. "Anatomy, Shoulder and Upper Limb, Median Nerve." https://www.ncbi.nlm.nih.gov/books/NBK448084/
StatPearls. "Carpal Tunnel Syndrome." https://www.ncbi.nlm.nih.gov/books/NBK448179/

Median Nerve